In general, a bill processing apparatus, which is one of the embodiments of the paper sheet processing apparatus, is incorporated into a service device such as a game medium rental machine installed in a game hall, a vending machine or a ticket-vending machine installed in a public space, or the like which identifies the validity of a bill inserted from a bill insertion slot by a user and provides various types of products and services in accordance with a value of the bill having been judged as valid.
Such a bill processing apparatus usually comprises a bill conveyance mechanism that conveys a bill inserted into the bill insertion slot, a bill identification part that conducts validity judgment (also referred to as “authenticity judgment”) whether the bill to be conveyed is valid or not, and a bill housing part (bill housing stacker) housing one bill after another having been validated by the bill identification part. This bill housing part also has a function as a safe, which is configured attachable to and removable from the apparatus main body, and comprises a placing plate, on which a plurality of bills are stacked and housed, pressing means (presser spring) for biasing the placing plate, and a presser plate for pressing a bill onto the placing plate against a biasing force by the presser spring such that the bill is guided and positioned thereon.
When the bill is guided between the placing plate and the presser plate, the presser plate is driven from an initial position to a pressing position on the placing plate side and presses bills onto the placing plate in the pressing position. The, as the presser plate is driven to return to the initial position, the bills having been pressed onto the placing plate are pushed back by the biasing force of the presser spring so that the uppermost bill of the bills hits and contacts a regulatory part whereby a plurality of bills are stacked and housed one after another on the placing plate.
Here, it is likely that the above-described bill housing part may fail in operation if too many bills are guided thereto such that detection means detecting that the number of bills on the placing plate reaches capacity limit is provided as disclosed in Patent Document 1. The detection means disclosed in Patent Document 1 detects a full state with the bills when a swinging lever is turned as bills are placed on a receiving plate (placing plate) inside a cassette in which the swinging lever has been rotatably installed. That is, the receiving plate is enabled to contact one end of the swinging lever when the full state with bills is reached, a slide lever engaged with the other end is raised by a lever action upon contacting the receiving plate, and the rising of the slide lever is detected by an optical sensor, having a light emitting part and alight receiving part, or a micro switch, etc., to detect that the receiving plate has become full with bills.    [Patent Document 1] Japanese unexamined utility model application publication No. H05-79679